This invention relates to switches, and more particularlyxe2x80x94but not exclusivelyxe2x80x94to switches for use in computer systems.
Over the last few decades, the use of computers has become widespread in business, education and at home. Modern computers are typically controllable by way of graphical user interfaces (GUIs) which allow a user to control the computer simply by manipulating a cursor to select commands from lists of alternatives displayed in pull-down menus on the screen of the computer.
The cursors employed in GUIs are designed to be controlled by a pointing device rather than a keyboard, although in practice control is often duplicated on the keyboard so that the computer can still be controlled if the pointing device should fail. Various pointing devices have been developed for control of a cursor in a GUI environment. The pointing devices are also typically provided with one or more switches or buttons for user selection of system functions. Separate switching modules may also be provided.
All of these previously proposed pointing devices may easily be manipulated by an able-bodied user to control a cursor in a GUI, and thus to control a computer. These modem computers can be controlled to perform a large number of functions such as speech replication and global communication through the internet and through modem to modem connections.
Given the great utility of modem computers, it would be highly desirable if they could be effectively utilised by mentally and physically disabled persons to perform a variety of different functions. To this end, various pointing devices have been developed which cater for the special needs of disabled users. These devices provide improved mechanisms for the control of an on-screen cursor, but they typically do not address the problems associated with the user selection of computer system functions.
For example, some mental and physical disabilities are such that the disabled person is incapable of illustrating the fine motor control necessary to depress keys of a keyboard or to depress buttons on a conventional pointing device to select functions of, or perform tasks on, a computer system. Other disabled persons suffer from problems associated with hand shake, for example, that cause a repeated depression of a button when they only wanted to press the button once. As a consequence of this, these disabled persons can be unable to effectively operate modern GUI-driven computers.
A means for alleviating these problems has previously been proposed in United Kingdom Patent Publication No. 2,339,632. This document describes an actuator for a switch which enables the resilient bias against which the actuator is movable to be adjusted to account for variations in the motor ability of different users.
Whilst the arrangement proposed in this document does alleviate the above mentioned problems, it has been noted that the actuator disclosed is rather large and can therefore take up a significant amount of desktop space. This is generally not too much of a problem when the switch is used at home or work on a desktop (when space considerations are not usually paramount), but can be a problem when used with a laptop computer in a mobile computing environment, for example, where space considerations are more important.
One might suppose that a solution to this new problem simply would be to reduce the size of the actuator disclosed in the above mentioned patent application.
However, such an approach would not be appropriate since by reducing the size of the actuator one would also severely limit the range and degree to which the resilient bias can be varied. The principle reason for this is that the preferred embodiment disclosed in this application includes a resiliently flexible beam which rides upon a pair of supports that can be moved with respect to one another to vary the distance between them, and hence vary the resistance to flexing of the beam. If one were to shorten the beam (as would be required if the actuator were to be reduced in size), then the degree to which the spacing between the supports could be varied would be reduced, and hence the range of resilient bias provided by the actuator would be correspondingly reduced.
A further problem is concerned with the fact that the preferred embodiment of the above mentioned actuator has a spiral track in which cams move, and reducing the size of the track could cause problems with the track becoming blocked by dirt or other foreign bodies.
A yet further problem is that reducing the size of the track would require a corresponding reduction in the size of the cams. If the cams were to made of the same material (as would be preferred to keep the cost of the device acceptably low), then there is a danger that they would no longer be sufficiently strong (after having been reduced in size) to survive the normal day to day stresses imposed upon the device during use.
It is apparent, therefore, that a new construction which avoids these problems would be advantageous. Accordingly, it is an object of the present invention to provide a switch which avoids and/or alleviates these problems.
In accordance with an aspect of the invention, there is provided a switch comprising an outer housing and an inner component; switch means operable to provide a signal upon depression of said outer housing; resilient biasing means located between the inner component and the outer housing to provide a force which biases the outer housing from the inner component; and means for varying the spacing between the inner component and the outer housing and hence the biasing force provided by said resilient biasing means.
This aspect of the invention alleviates the problems mentioned above by providing a relatively compact switch that allows the initial spacing of the outer housing and inner component to be varied to vary the biasing force provided by the resilient biasing means. This means that for those users who lack sufficient strength to effectively utilise conventional switches, the resistive force (i.e. the biasing force) can be decreased so that a lesser pressure is required. Similarly, for those persons who suffer from hand shake, for example, the resistive force (i.e. the bias force) can be increased so that a definite depressive movement is required to activate the switch and so that relatively small hand movements, that could be cased by a hand tremor for example, do not cause the switch to be activated.
Furthermore, by adopting a this arrangement in preference to the arrangement disclosed in the above mentioned patent application it is possible to provide a switch which is significantly smaller and more compact than the previously proposed switch.
Preferably, the switch comprises a base having an inner retaining member upstanding therefrom.
Preferably, the inner component is mounted on and movable with respect to the inner retaining member.
Preferably, the inner component has a threaded inner surface which is screw-threadedly engageable with a threaded outer surface portion of the inner retaining member.
Preferably, the spacing varying means comprises the threaded inner surface of the inner component and the threaded outer surface of said inner retaining member.
Preferably, rotation of the outer housing causes the biasing force provided by said resilient biasing means to vary.
Preferably, the inner component rotates with the outer housing.
Preferably, the inner component comprises a plurality of laterally extending (preferably laterally outwardly extending) tabs or lugs locatable in respective longitudinal grooves formed in an inside lateral surface of said outer housing.
Preferably, the grooves permit longitudinal movement of the tabs or lugs to allow depression of the outer housing to cause operation of the switch means.
Preferably, the base has an outer retaining member upstanding therefrom, the outer retaining member having a transversely extending flange against which a transversely extending flange of the outer housing can abut to resist decoupling of the outer housing from the base.
Preferably, the resilient biasing means comprises a spring.
Preferably, the switch is substantially circular.
Preferably, variation in the spacing of the outer housing and inner component is accomplished whilst maintaining a substantially constant spacing between the outer housing and the base.
In accordance with a further embodiment of the invention, there is provided a switch for a computer system, the switch comprising: a base; a retaining member upstanding from the base, an inner component rotatably and screw-threadedly engaged with the retaining member; an outer housing connected for rotational movement with the inner component; resilient biasing means provided between the outer housing and inner component to bias one from the other; and switch means operable to provide a signal upon depression of said outer housing; the arrangement being such that rotation of the outer housing causes the spacing between the inner component and the outer housing and hence the biasing force provided by said resilient biasing means to vary.
A further aspect of the invention relates to use of a switch as described herein as an item selection tool for a computer system.